Circuit breaker with high speed interrupter



April 23, 1968 R. c. VAN SICKLE 3,380,005

CIRCUIT BREAKER WITH HIGH SPEED INTERRUPTER Filed Feb. 16, 1965 4 Sheets-Sheet 1 WITNESSES: INVENTQR @bwu$\ .G Roswell C. VonS|ck|e Wham ATTORNEY CIRC UIT BREAKER WITH HIGH SPEED INTEHRUPTER Filed Feb. 16, 1965 April 23, 1968 R. c. VAN SICKLE 4 Sheets-Sheet 2 FIG.2.

PM allllf ll- April 23,1968 c, VAN s c E 3,380,005

CIRCUIT BREAKER WITH HIGH SPEED INTERRUPTER Filed Feb. 16, 1965 4 Sheets-Sheet 4 To TERMINAL 49 65 CONNECTOR RESISTANCE IN MAIN CIRCUIT CLQSED-LOOP BETWEEN M CONDUCTOR CIRCUIT ANDA N INDUCTANCE CAUSED BY CLOSED-LOQP\ LEAKAGE FLUX OUTSIDE CONDUCTOR THE MAIN AIR GAP CLOSED-LOOP CONDUCTOR CIRCUIT SHADING COIL CIRCUIT INDUCTANCE CAUSED BY LEAKAGE FLUX OUTSIDE MUTUA BETWEEN CLOSED- I LOOP CONDUCTOR NDUCTANCES AND SHADING COIL BETWEEN MAIN/ THE MAIN AIR GAP CIRCUIT AND SHADING COIL RESISTANCE IN SHADING COIL United States Patent 3,380,005 CIRCUIT BREAKER WITH HIGH SPEED INTERRUPTER Roswell C. Van Sickle, Wilkinsburg, Pa, assiguor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Feb. 16, 1965, Ser. No. 432,984

14 Claims. (Cl. 335-19) ABSTRACT OF THE DISCLOSURE An alternating-current circuit interrupter has a main current path and an auxiliary electrically-parallel current path, the latter being open in the closed position of the interrupter. A synchronous operator opens the auxiliary current path at a current zero while the main current path has already been opened due to the operating linkage construction. A linearly-movable armature with two oppositely-extending closed loop portions and carrying the movable auxiliary contact, moves through a idiametrical air gap in the magnet structure, which encircles the auxiliary current path. Shading coils or a conducting plate in the magnetic air gap assists in reducing the leakage inductance of the closed loop in the armature closed loop circuit.

This invention relates, generally, to circuit breakers and, more particularly, to a circuit breaker having interrupting contacts operated at high speed and opened at substantially a current zero.

Previously proposed schemes for operating circuit breakers of the synchronous type have required the provision of some means between the synchronous operator and the interrupter for utilizing the force developed by the operator to control the operation of the contact members of the interrupter. This has increased the cost of the apparatus as well as the time required for an interruption after the occurrence of a short circuit.

An object of this invention is to provide a circuit breaker having contacts operated at high speed and opened a fraction of a cycle before a current zero.

Another object of the invention is to provide a synchronous interrupter having a movable contact member formed integrally with the driving member of the synchronous operator for the interrupter.

A further object of the invention is to prevent high iron losses in the magnetic circuit for the synchronous operator of a synchronous interrupter.

Still another object of the invention is to reduce the inductance of the closed circuit of the synchronous operator for the synchronous interrupter.

A still further object of the invention is to increase the driving force of the armature member of the synchronous operator.

Another object of the invention is to utilize force produced by current flowing through an interrupter to open the contact members of the interrupter at a short predetermined interval before a current zero.

A further object of the invention is to provide a device energized by an alternating current electrical circuit and capable of exerting a mechanical force which is very strong immediately before a current zero, and which reverses in direction if the current flows in the opposite direction after current zero.

Other objects of the invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with one embodiment of the invention, an interrupter for a circuit breaker has a main path and an auxiliary path through the interrupter. The movable contact of the auxiliary path is formed integrally with the armature member of a synchronous operator having a "ice magnetic circuit energized by the current flowing through the auxiliary path. The auxiliary path is open when the breaker is standing closed to insure that the main contacts carry the current and that high iron losses do not occur in the auxiliary circuit. When a short-circuit current is to be interrupted, a small movement of the operating linkage closes the auxiliary circuit. The main contacts are then opened, transferring the current to the auxiliary contacts which are opened slightly before a current zero by the synchronous operator, the effectiveness of which is increased by providing shading coils in the pole faces of the air gaps in the magnetic circuit.

For a better understanding of the nature and objects of the invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a diagrammatic view of an interrupter for a circuit breaker embodying principal features of the invention;

FIG. 2 is a view, in plan, of a portion of a synchronous operator for the interrupter shown in FIG. 1;

FIG. 3 is a view, in side elevation, of the structure shown in FIG. 2;

FIGS. 4 and 5 are views, in side and end elevation, respectively, of a modified synchronous operator;

FIGS. 6, 7 and 8 are diagrammatic views illustrating electrical circuits for the modified structure shown in FIGS. 4 and 5; and,

FIG. 9 is a diagrammatic view of a modification of the structure shown in FIGS. 1 and 2.

Referring to the drawings, and particularly to FIG. 1, the interrupting structure shown therein may be utilized in a circuit breaker of either a multi-break or a singlebreak type. Since the general construction of the circuit breaker may be of a type well known in the art, only the structure of the interrupter is shown in this application. The interrupter has a main path 11 and an auxiliary path 12 which are connected in parallel-circuit relation under certain conditions as will be described more fully hereinafter.

The main path 11 includes a relatively stationary contact member 13 and a movable contact member 14. When in the closed position the member 14 engages a contact ring 15 which may be threaded on the lower end of the member 13. Contact fingers 16 slidably engage the movable contact member 14. The contact fin-gers 16 may be connected to a terminal connector (not shown) on the circuit breaker. Likewise, the member 13 may be connected to a terminal connector on the circuit breaker.

The auxiliary path 12 includes a relatively stationary contact member 17, a movable con-tact member 18 and contact fingers 19 which slidably engage an armature member 21 formed integrally with the movable contact member 18. The con-tact members 17 and 18 are preferably of the tubular type. The member 17 is connected to the member 16 of the main path 11 by a conductor 22.

A gas chamber 23 surrounds the contact members 17 and 18. The chamber 23 is charged with an interrupting gas, such as sulfur hexafluoride (SP gals before the contact members 17 and 18 are separated during an interrupting operation. The admission of the gas into the chamber 23 from a high pressure storage tank (not shown) is controlled by an inlet valve 24 which may be operated either electrically or mechanically in a manner well known in the art.

The main contact member 14 is opened and closed and :the auxiliary contact member 18 is closed by a cross link 25 which is connected to an operating mechanism (not shown) by an operating linkage 26. The link 25 may comprise two spaced cross arms which are joined by pins 27 and 28. One end of the cross link is pivotally connected by the pin 28 to a member 29 which is attached to the lower end of the main movable contact member 14. The operating mechanism may be of a type well known in the art and so constructed that the main contacts are closed first and opened first.

As shown most clearly in FIG. 2, each cross arm 25 has an angularly extending contact portion 31 disposed to engage the lower ends of two of the contact fingers 19. Thus, the parallel circuit is established through the auxiliary path 12 when the lower ends 19a of the contact fingens 19 engage the cross arms 25, which are connected to the main movable contact member 14. However, when the breaker is standing fully closed, as shown in FIG. 1, the contact fingers .19 are disengaged from the cross arms 25 and the circuit through the auxiliary path is opened to insure that the main contacts carry all of the current and that high iron losses do not occur in the auxiliary circuit, as will be described more fully hereinafter.

The cross link of the operating linkage between the main and auxiliary contacts travels only a short distance, for example, 0.6 to 1.0 inch. In its open position it holds the main contacts open and makes contact with the lower ends 19a of the fingers 19 in the auxiliary circuit. As it moves toward the closed position it separates from these fingers 19a to make a second gap in the auxiliary circuit. Further movement to an over-travel position causes it to engage a projection 32 on the armature 21 carrying the movable auxiliary contact 18 and to move it toward the stationary auxiliary contact 17. During this movement a projection 33 on the operating linkage 26 engages a latch lever 34 which is pivotally attached to a spring support 35 by a pin 36. The lever 34 engages a pin 37 on a downwardly extending projection 38 of a combined latch support and spring member 39 having spring portions 41 thereon which engage corresponding spring portions 42 on the support member 35. A latch 43 is pivotally mounted on the member 39 by means of a pin 44. The latch 43 is biased counter-clockwise by a compression spring 45. Thus, when the lever 34 moves the latch 43 downwardly away from the projection 32, the latch moves into a position where it is permited to engage the projection 32 when the operating link 25 returns from its over-travel position. As the closing force of the operating mechanism is released the operating link 25 returns a short distance from its'over-travel position, thereby releasing the latch lever 34 and the restraint on the heavy biasing spring 41. The heavy biasing spring now presses the auxiliary contacts together through the latch 43 which engages the projection 32. However, no current flows through the auxiliary circuit because of the gaps between the lower ends 19a of the contact fingers 19 and the contacts 31 on the cross arms 25. As explained hereinbefore, the main contacts 14, 15 carry all of the current While the breaker is standing fully closed.

In order that the arc drawn during opening of the circuit breaker may be extinguished at current zero a synchronous operator is provided for opening the auxiliary contact members. The synchronous operator comprises a generally cylindrical core 46 composed of laminated magnetic material, such as iron, having two oppositely disposed air gaps 47 therein and a central opening 48 extending through the core, and the armature 21 which includes two oppositely extending closed loop circuits 49.

As previously explained, the armature 21 and the loop circuits 49 are preferably formed integrally with the movable contact member 18. However, they may be formed separately and attached to the moving contact member 18. The armature is of a light construction, preferably composed of aluminum or magnesium. Because of the large forces required for high acceleration of the contact 18, the stresses are high and a thin web 51 is provided inside each of the closed loops 49. Holes or depressions may be made in the web to remove material that is not needed for strength. When the auxiliary contact members 17, 18 are closed, the loop circuits are inserted part way in the magnetic circuit as shown in FIG. 3. The moving contact 18 and the armature 21 are -a unit movable rectilinearly in the magnetic circuit. The movement is guided by a guide member 52 and guide rollers 53 shown in FIGS. 2 and 3.

The arcing contacts 17, 18 both moving and stationary, are tubular with internal venting so that the arc terminals are drawn into the tubes and no arc terminals remain near the ends of the contacts to serve as ion sources during the time the voltage is recovering across the contacts 17, 18. The are terminals move down the tubes and elongate the are faster than the contacts'17, 18 separate. As shown in FIG. 1, vents 54 are provided in the stationary contact 17, and the moving contact 18 is vented through the bottom of the contact.

The magnetic circuit has two air gaps in series and is energized by the current to be interrupted which flows through the contact fingers 19, which extend through the central opening 48 in the magnetic core, to the conducting cross arm 25 of the operating linkage. By way of example, the iron circuit will be saturated when the current is about 26,000 amperes. Consequently, during a 50,000 ampere RMS fault the magnetic circuit without an armature would be saturated except for the time from about 0.0010 second before current zero to about 0.0010 second after current zero. During this time the flux would change at about 10 times the rate it changes during the rest of the cycle when the iron is saturated. Consequently, during most of the cycle the voltage induced in the short circuited loops 49 is about of the voltage induced during the 0.0020-second time interval near current zero. The armature 21 is biased closed by a force adequate to overcome the separating forces at this time. However, the currents induced in the short circuited loops 49 will rise rapidly when the iron circuit ceases to be saturated and the flux tends to change at a 10 times higher rate.

When the breaker is to be opened to interrupt a short circuit current flowing through it, the operating linkage 26 is moved downwardly and the high speed inlet valve 24 is opened to admit gas into the chamber 23. However, relatively little gas escapes while the auxiliary contacts 17, 18 remain closed.

A small movement of the operating linkage 26 closes the auxiliary circuit 12 by engaging the cross link contacts 31 with their cooperating fingers 19a. The main contacts 14, 15 are then opened and the short circuit current is transferred to the auxiliary circuit 12 which is able to interrupt it at a current zero, but which has high speed synchronized contacts 17, 18 which keep are power and energy to a minimum.

The auxiliary interrupter is momentarily held in the closed position by the latch 43 which is biased by the spring 41 with a force greater than the total opening forces acting on the armature 21 and auxiliary moving contact 18. The latch 43 is released by the pin 27 on the cross arm 25 after the cross arm has moved to a position which permits the armature 21 to complete its opening stroke without any interference. Also, the main contacts 13 and 14 are separated sufficiently to increase the dielectric strength between them, so that a circuit cannot be established through them by any transient recovery voltage appearing across the interrupter subsequent to the interruption of the current by the auxiliary contacts 17, 18.

In the structure shown, the sum of the two currents in the closed loops 49 rises almost as rapidly as the instantaneous current in the energizing circuit decreases. Consequently, the opening force produced on the parts of the loops 49 which are located in the magnetic field increases rapidly and the armature 21 with its attached or integral moving contact 18 is accelerated to the open position. Calculations indicate that with the construction shown a contact separation of one-half inch will be reached by the time of current zero.

If the arc is not extinguished at current Zero the flux reverses and continues to change at the same high rate. This reversal of the flux reverses the accelerating force and while the short circuit current is increasing the force will close the contacts 17, 18. Because the current in the loop 49 is already high, and the opening motion is limited by a stop, the closing can occur even faster than the opening and the are energy is kept small. When the short circuit current begins its cyclical decrease, the currents in the loops 49 reverse and an opening force is produced, but it does not cause the contacts 17, 18 to separate until, as previously described, the instantaneous current in the auxiliary circuit 12 no longer produces saturation in the iron.

The device works over a range of current because at lower currents the point of saturation of the iron is reached at a longer time before current zero and accelerating forces increase at a correspondingly lower rate, but adequate contact separation is obtained at current hero. However, at very low currents the opening forces would not be sufficient to overcome the restraining forces determined in magnitude by the need for functioning at high short circuit currents. At these currents synchronous operation is not necessary for successful interruption by the arc, and the armature 21 may be opened mechanically by the operating linkage.

One of the difficulties to be overcome in building a synchronous switch of the type hereinbefore described is the inductance of the short circuited turn or closed loop conductor 49 of the armature 21. This circuit has a mutual inductance linked with the main circuit 46 which supplies the driving EMF and a leakage inductance which opposes any change of current in the closed loop conductor 49. Because of the single turn, the limited flux carrying ability of the iron circuit below saturation, and the limits in practical physical size, the voltage induced in the short circuited turn or closed loop conductor 49 is limited to a few volts. The part of this voltage consumed in increasing the current in the loop is directly proportional to the leakage inductance of this circut and is relatively large. Consequently, reducing this leakage inductance is important.

Much of the leakage inductance of the armature closed loop circuit 49 is produced by the Flux A, see FIG. 5, which encircles the closed loop 49 through a path which crosses the air gap twice, but for most of its length is through iron. Other leakage inductance is caused by the leakage flux which encircles the closed loop 49 through a path which crosses the air gap once and returns by a longer air path between the sides of the iron core. Reducing these fluxes reduces the leakage inductance.

Since these are changing fluxes, the rate at which they are increased can be reduced by placing in their paths material of high electrical conductivity which will permit currents to be formed in them to resist the change in flux. This can be done in at least two ways. The first is a plate 61 of high conductivity material, such as copper, placed in the paths of the fringing flux of the air gaps. As shown in FIGS. 4 and 5, the plates 61 are placed on the sides of the iron core adjacent the air gap. These plates each form short-circuited current paths around leakage flux and decrease the effective inductance of the closed loop conductor 49.

Another approach is to encircle the flux entering the portion of the pole face not covered in the closed position by the closed loop 49 in FIGS. 4 and 5 by a high conductivity loop '62. This is accomplished by providing a short-circuited turn in one pole face of each air gap in the magnetic circuit or preferably by providing a turn in both pole faces of each gap. As shown, the turn 62 is so located that it encircles the part of the pole face not covered by the closed loop conductor 49' of the armature 21' when the armature and is associated contact 18' are in the closed position. Each turn 62 is disposed in a 6 plane parallel to the plane of the closed loop conductor 49'.

The short'circuited turn 62 in the pole face is somewhat similar to that used on AC solenoids for causing a phase shift in a component of the flux, and commonly known as a shading coil. Consequently, this short-circuited turn will be referred to as a shading coil in the following description.

This shading coil performs two useful functions. As already indicated, its primary purpose is to reduce the leakage inductance. By having a low resistance shading coil a current will be induced in it which is nearly equal and opposite to the current in the closed loop conductor 49' of the armature 21'. Only the difference between the two currents is available to produce the Flux A and consequently the rate at which current can be increased in the closed loop conductor 49' of the armature 21' is increased.

The second useful function of the shading coil 62 is to increase the force which opens the contacts prior to current zero. As in AC. (alternating current) solenoids, it causes the flux in the area covered by it to lag the flux in the main part of the circuit. Since the force on the closed loop 49' is proportional to the product of the current and the flux density through which it passes, this delay in the rate at which the flux in the part of the pole face surrounded by the shading coil 62 decreases as the current approaches zero, will appreciably increase the product of the current magnitude and the flux density, thereby increasing the force on the moving member 21' during the critical interval before current zero.

The electrical circuits are shown in FIGS. 6, 7 and 8. FIG. 6 shows diagrammatically a cross section of the structure. The main current flows through a path which is surrounded by the flux path of the laminated iron core. Between the pole faces of the air gaps 47 are the closed loop conductors 49 of the armature, shown by an equivalent single turn, and on the pole faces are shading coils, also shown by one turn 62.

FIG. 7 shows the electrical circuit of a synchronous switch without a shading coil 62. A mutual inductance between the main circuit and the closed loop conductor 49' of the armature 21 provides the driving 'EMF in the closed loop conductor 49'. The circuit has resistance and leakage inductance which oppose any increase in current. The diagram shows this leakage inductance divided into two parts, one produced by the leakage flux in the pole faces and one by the leakage flux around the rest of the conductor. The part around the conductor between the pole faces is about 10 times as large 'as the other part.

FIG. 8 shows the electrical circuit of a synchronous switch utilizing the shading coil 62. The closed loop conductor 49 and the shading coil 62 both have electrical circuits with a mutual coupling and both are driven by the current in the main circuit by a mutual coupling to it. The most of the leakage flux of the closed loop conductor which passes through the gap is now coupled with the shading coil 62 and instead of forming a leakage inductance now forms a mutual inductance. The effect is to greatly modify this flux. Depending upon the circuit constants, the Flux A may be in either direction and may even induce a voltage in the closed loop conductor 49' to increase the current. Consequently, the shading oil 62 can greatly reduce the leakage inductance of the closed loop conductor 49 and thereby aid in producing a device in which the current can rise rapidly in the closed loop conductor 49' of the armature 21'.

As explained hereinbefore, a further purpose of the present invention is to increase the driving force produced by the closed loop conductors of the armature and thereby provide faster operation. The force is proportional to the product of the current in the closed loop conductor and to the flux in the air gap. The manner in 7 which the current is made to increase more rapidly has been described.

The flux in the air gap is made more effective by the addition of the shading coil 62. In the device without the shading coil hereinbefore described the flux acting on the conductor varied almost directly with the current in the main circuit when the flux in the iron circuit was below saturation. Consequently, 'as the current in the main circuit approached zero the flux decreased rapidly reaching zero when the current reached zero. By the time the current in the closed loop conductor reached high value the flux had decreased to perhaps half its saturation value.

As shown in FIGS. 4 and 5, the shading coil 62 is disposed in a plane parallel to the plane of the closed loop conductor 49' and covers the part of the pole face providing the field which reacts with the current in the closed loop conductor. The shading coil 62 delays the decrease in this field and thereby increases the product of the current and flux. Consequently, the shading coil increases the driving force not only by increasing the rate at which current increases in the closed loop conductor, but also by strengthening the magnetic field with which the current reacts.

The structure shown in FIG. 9 is similar to that shown in FIGURES l, 2 and 3 except the armature 21 has only one closed loop conductor 49 and it is pivotally mounted on a stationary pivot 65. Thus, the loop conductor 49' is movable in the 'air gap 47' in the plane of the loop conductor. A contact member 66 is carried by the cross arm 25 but insulated from the cross arm by insulation 67. The member 66 is connected to a conductor 68 which extends through the core 46', thereby energizing the magnetic core when the contact member 66 engages the contact finger 19a during opening of the breaker. Other parts of the interrupter are similar to those previously described and the operation is similar to the manner of operation hereinbefore described.

Pivotally supporting the armature reduces the weight which must be moved by the force developed in the closed loop conductor. In this manner the inertia of the device is reduced and the speed of operation is increased, thereby improving the performance of the synchronous operator.

From the foregoing description it is apparent that the present interrupter has the following advantages:

(1) A contact of adequate size to switch heavy short circuit currents.

(2) The removal of arc terminals from spaces which have high electrical stresses during the transient recovery voltage period.

(3) A gas chamber immediately adjacent to the arc to provide a quick and adequate supply of arc extinguishing medium.

(4) Short vent paths to provide high velocity gas flow.

(5) A contact which is restrained until it can open freely for its full travel.

(6) A contact which has a high acceleration and can open /2 inch in 0.0010 second or less.

(7) An interrupter which is out of the circuit except during an opening operation and consequently does not have high iron losses.

(8) A simple lightweight, rigid member combining armature and moving contact to act at high speed.

(9) Adequate contact guiding without appreciable friction.

(10) A device having sufiicient driving force to insure separation of the contact members of the interrupter.

Since numerous changes may be made in the above described construction and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the subject matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. In a circuit interrupter, in combination, a magnetic circuit having diametrically disposed air gaps therein, said magnetic circuit being energized by the current to be interrupted and magnetically saturable at high fault currents, an armature comprising two closed loop conductors movable rectilinearly in said air gaps, and a movable contact member carried by said armature.

2. In a circuit interrupter, in combination, a relatively stationary contact member, a movable contact member engaging the stationary contact member to conduct current therethrough, a magnetic circuit energized by said current and magnetically saturable at high fault currents, said magnetic circuit having oppositely disposed diametrically arranged air gaps therein, an armature comprising two oppositely extending closed loop conductors movable rectilinearly in said air gaps, and said movable contact member being movable with said armature to interrupt the circuit through the contact members.

3. In a circuit interrupter, in combination, a relatively stationary contact member, a movable contact member engaging the stationary contact member to conduct current therethrough, a magnetic circuit energized by said current and magnetically saturable at high fault currents, said magnetic circuit having oppositely disposed diametrically-arranged air gaps therein, an armature comprising two oppositely extending closed loop conductors supporting said movable contact member, and said conductors being movable rectilinearly in said air gaps to interrupt the circuit through the contact members.

4. A synchronous operator for a circuit interrupter comprising a generally cylindrical core of magnetic material having oppositely disposed diametrically-arranged air gaps therein and magnetically saturable at high fault currents, a contact member disposed in line with the central axis of the cylindrical core and carrying the current to be interrupted, said core being energized by said current, an armature comprising oppositely extending closed loop conductors supporting the contact member, and said conductors being moved rectilinearly in said air gaps to actuate the contact member to open and closed positions.

5. A synchronous operator for a circuit interrupter comprising a generally cylindrical core of magnetic material having oppositely disposed diametrically-arranged air gaps therein, a contact member disposed in line with the central axis of the cylindrical core and carrying the current to be interrupted, said core being energized by said current and magnetically saturable at high fault currents, an armature comprising oppositely extending closed loop conductors and supporting the contact member, said conductors being moved rectilinearly in said air gaps to actuatethe contact member to open and closed positions, and guide means for guiding the movement of the annature member.

6. A synchronous operator for a circuit interrupter comprising a generally cylindrical core of magnetic material having oppositely disposed diametrically-arranged air gaps therein, a contact member disposed in line with the central axis of the cylindrical core and carrying the current to be interrupted, said core being energized by said current and magnetically saturable at high fault currents, an armature comprising oppositely extending closed loop conductors and supporting the contact member, said conductors being moved rectilinearly in said air gaps to actuate the contact member to open and closed positions, and a reinforcing web inside each closed loop conductor.

7. A synchronous operator for a circuit interrupter comprising a generally cylindrical core of magnetic material having oppositely disposed diametrically-arranged air gaps therein, a contact member disposed in line with the central axis of the cylindrical core and carrying the current to be interrupted, said core being energized by said current and magnetically saturable at high fault currents, an armature comprising oppositely extending closed loop conductors and supporting the contact member, said conductors being moved rectilinearly in said air gaps to actuate the contact member to open and closed positions, and a short-circuited turn of conducting material disposed on a pole face of the core at an air gap in a plane parallel to the plane of the closed loop conductor in the air gap.

8. A synchronous operator for a circuit interrupter comprising a generally cylindrical core of magnetic material having oppositely disposed diametrically-arranged air gaps therein, a contact member disposed in line with the central axis of the cylindrical core and carrying the current to be interrupted, said core being energized by said current and magnetically saturable at high fault currents, an armature comprising oppositely extending closed loop conductors carrying the contact member, said conductors being moved rectilinearly in said air gaps to actuate the contact member to open and closed positions, short-circuited turns of conducting material disposed on opposite faces of the core at each air gap in planes parallel to the plane of the closed loop conductor in the air gap, and said turns being located to encircle the portions of the pole faces of the core not encircled by the closed loop conductors when they are in the closed position of the contact member.

9. A synchronous operator for a circuit interrupter comprising a generally cylindrical core of magnetic material having oppositely disposed diametrically-arranged air gaps therein, a contact member disposed in line with the central axis of the cylindrical core and carrying the current to be interrupted, said core being energized by said current and magnetically saturable at high fault currents, an armature comprising oppositely extending closed loop conductors and carrying the contact member, said conductors being moved rectilinearly in said air gaps to actuate the contact member to open and closed positions, a short-circuited turn of conducting material disposed on a pole face of the core at an air gap in a plane parallel to the plane of the closed loop conductor in the air gap, and a plate of conducting material disposed on the side of the core adjacent the air gap.

10. In a circuit breaker, in combination, main contact means, auxiliary contact means connected in parallelcircuit relation to the main contact means, means including a cross arm for closing the main and the auxiliary movable contact means, contact finger means in the auxiliary circuit which open the auxiliary circuit at the end of the closing operation, means for opening the main contact means at the beginning of the opening stroke and closing for opening the auxiliary contact means after opening of the main contact means.

11. In a circuit breaker, in combination, main contact means, auxiliary contact means connected in parallel-circuit relation to the main contact means, means including a cross arm for closing the main and the auxiliary contact means, means for opening the main contact means at the beginning of the opening stroke, contact fingers for establishing said parallel auxiliary connection through said cross arm during opening operation of the cross arm, said parallel auxiliary connection being opened While the main contacts are fully closed, by separation of the contact fingers from the cross-arm, and a synchronous operator for opening the auxiliary contacts after the opening of the main contacts.

12. In a circuit breaker, in combination, main contact means, auxiliary contact means connected in parallelcircuit relation to the main contact means, means including a cross arm for closing the main and the auxiliary contact means, means for opening the main contact means at the beginning of the opening stroke, contact fingers for establishing said parallel auxiliary connection through said cross arm during opening operation of the cross arm, said parallel auxiliary connection being opened while the main contacts are fully closed, latch means for retaining the auxiliary contacts closed, said latch means being released by the opening motion of the cross arm after the opening of the main contacts, and a synchronous operator for opening the auxiliary contacts after the releasing of the latch means.

13. A circuit interrupter comprising a generally cylindrical magnetic core having oppositely disposed diametrically-arranged air gaps therein and magnetically saturable at high fault currents, current conducting means extending through the core and carrying the current to be interrupted, an armature including oppositely extending closed loop conductors movable rectilinearly in said air gaps, and contact means electrically connected to the conducting means and movable with the armature to interrupt the current flowing in the conducting means.

14. The combination of claim 10, wherein the synchronous operator comprises a saturating magnetic core having an air gap therein, said magnetic core being energized by an alternating current electrical circuit, an armature having a closed loop conductor pivotally disposed in the air gap and movable in the plane of the loop conductor to exert a mechanical force in one direction immediately before a current zero and in the opposite direction when the energizing current reverses after current zero.

References Cited UNITED STATES PATENTS 3,174,019 3/1965 Jansson 200-146 3,211,868 10/1965 Barkan et a1. 200--146 3,215,866 12/1965 Kesselring 200-448 BERNARD A. GILHEANY, Primary Examiner.

H. BROOME, Assistant Examiner. 

